JP5573407B2 - Metal base substrate - Google Patents

Description

  The present invention relates to a metal base substrate that provides a heat dissipation function while mounting a semiconductor element or the like, and more particularly to a metal base substrate that combines a ceramic layer and a metal plate.

  The metal base substrate has a relatively high heat dissipation function, and is advantageously used for mounting an electronic component that requires heat dissipation, such as a semiconductor element.

  As a technique of interest to the present invention, Japanese Patent Publication No. 2002-505805 (Patent Document 1) discloses a ceramic multilayer obtained by firing a surface of a metal support having an adhesive glass provided with a green tape layer. A circuit board is described.

  However, in the case of firing in a state where a ceramic layer (green tape layer) is provided only on one main surface of a metal plate (metal support) as in the case of Patent Document 1, particularly as shown in FIG. It is fully conceivable that there is a problem that the entire metal base substrate (ceramic multilayer circuit substrate) is warped due to a difference in thermal expansion coefficient with respect to the substrate.

  In this regard, in Japanese Patent Application Laid-Open No. 2003-124584 (Patent Document 2), a metal circuit board is formed on one main surface of a substrate formed by sandwiching a Cu plate or a Cu alloy plate between two silicon nitride plates, A ceramic circuit board is described in which a metal plate is bonded to the other main surface.

  Describing in more detail with reference to FIG. 1 of Patent Document 2, a direct bonding method or an active metal method is performed by sandwiching a Cu plate 4, which is a metal plate, between fired silicon nitride plates 2, which are ceramic layers. The base 6 is produced by bonding using the silicon nitride plate, thereby preventing the silicon nitride plate from being cracked by the thermal stress generated during the bonding. Further, the metal plate 5 is bonded to the lower surface of the base 6 so that the metal plate 5 functions as a heat sink.

  If the technique described in Patent Document 2 is used, the warp of the metal base substrate (base 6) due to the difference in thermal expansion coefficient is suppressed by forming ceramic layers on the upper and lower surfaces of the metal plate (Cu plate 4 or the like). be able to.

  However, in the structure described in Patent Document 2, the metal base substrate (base 6) uses a metal plate (Cu plate 4 or the like) having high thermal conductivity, but is not connected to the heat sink (metal plate 5). Since a ceramic layer (silicon nitride plate 2) is interposed in the plate, there is a problem in that heat dissipation is reduced due to the presence of the ceramic layer on the lower surface.

Special Table 2002-505805 JP 2003-124584 A

  Accordingly, an object of the present invention is to provide a structure of a metal base substrate that can suppress warpage that may occur during manufacturing and can improve thermal conductivity to a heat sink.

The present invention includes a metal plate having first and second main surfaces facing each other, a first ceramic layer formed on the first main surface of the metal plate, and a second main surface of the metal plate. In order to solve the technical problem described above, the second ceramic layer has a frame shape on the second main surface. together with at least comprising a frame-like portion positioned along the region, have a opening for exposing a portion of the second major surface in a region surrounded by the frame-like portion, the surface of the opening side of the metal base substrate It is characterized by being located outside the second main surface .

  According to the present invention, the first and second ceramic layers are formed on the first and second main surfaces of the metal plate, respectively, and the frame-like portion is formed while the second ceramic layer forms the opening. Since it has, the curvature of a metal base board | substrate can be suppressed.

  Further, since the second ceramic layer has an opening exposing a part of the second main surface in the region surrounded by the frame-shaped portion, the heat sink can be directly bonded to the metal plate through this opening. Therefore, the heat dissipation of the metal base substrate can be improved.

  In this invention, if the frame-like portion of the second ceramic layer is positioned so as to cover the peripheral edge without leaving a margin at the peripheral edge of the second main surface of the metal plate, the frame includes the peripheral edge of the metal plate. Thus, warpage of the entire metal base substrate can be suppressed.

  When the second ceramic layer further includes a lattice-like portion extending in a lattice shape in a region surrounded by the frame-like portion, and the openings are formed between the lattices of the lattice-like portion and distributed in an island shape, Higher heat dissipation can be realized while sufficiently exhibiting the effect of suppressing warpage by the lattice-like portion.

1 shows a metal base substrate 1 according to a first embodiment of the present invention, where (1) is a sectional view and (2) is a bottom view. 1A and 1B show a metal base substrate 1a according to a second embodiment of the present invention, in which (1) is a cross-sectional view and (2) is a bottom view. It is sectional drawing which shows the electronic component apparatus 11 comprised using the metal base substrate 1a shown in FIG. The metal base substrate 21 which concerns on the sample 1 which it is going to produce in Experimental example 1 is shown, (1) is sectional drawing, (2) is a bottom view. It is sectional drawing which shows the metal base substrate 31 which concerns on the sample 2 which is going to produce in Experimental example 1. FIG.

  A metal base substrate 1 according to a first embodiment of the present invention will be described with reference to FIG.

  The metal base substrate 1 includes a metal plate 4 having first and second main surfaces 2 and 3 facing each other, a first ceramic layer 5 formed on the first main surface 2 of the metal plate 4, Similarly, a second ceramic layer 6 formed on the second main surface 3 is provided. The metal plate 4 is preferably composed mainly of a metal having high thermal conductivity, for example, aluminum, copper or silver, in order to effectively exert its function. Among them, when the ceramic layers 5 and 6 are formed by co-firing an unfired low-temperature sintered ceramic layer with the metal plate 4, the metal plate 4 is mainly composed of copper or silver, particularly copper. Is preferred.

  Although not shown in FIG. 1, a semiconductor element such as an IC and other electronic components are mounted on the first ceramic layer 5. Therefore, several surface conductors 7 are formed on the first ceramic layer 5. Although not shown, the first ceramic layer 5 may have a laminated structure including a plurality of ceramic layers, and an internal conductor for wiring or the like may be provided therein.

The second ceramic layer 6 includes at least a frame-shaped portion 8 positioned along the frame-shaped region on the second main surface 3, and the second main surface 3 in a region surrounded by the frame-shaped portion 8. Has an opening 9 for exposing a part of the opening 9. In the embodiment shown in FIG. 1, the second ceramic layer 6 is constituted only by the frame-shaped portion 8. Further, as can be seen from FIG. 1 (1), the surface of the metal base substrate 1 on the opening 9 side is located outside the second main surface 3.

  Further, the frame-shaped portion 8 may have a margin at the peripheral edge of the second main surface 3, but it is preferable that the frame-shaped portion 8 is positioned so as to cover the peripheral edge without leaving a margin at the peripheral edge. With this configuration, it is possible to suppress warpage of the entire metal base substrate 1 including the peripheral portion of the metal plate 4.

  Although not shown, the second ceramic layer 6 may also have a laminated structure composed of a plurality of ceramic layers, and an internal conductor for wiring or the like may be provided therein.

  In addition, although the frame-shaped part 8 may have a notch or a parting part in the part, it is preferable not to have a notch or parting part.

  The opening 9 formed in the second ceramic layer 6 makes it possible to join a heat sink (not shown in FIG. 1) to the metal plate 4 by, for example, soldering, thereby improving the heat dissipation of the metal base substrate 1. Can be made.

  The metal base substrate 1 is manufactured as follows, for example.

  First, a metal plate 4 is prepared, and a green ceramic green layer to be the first and second ceramic layers 5 and 6 is formed on the first and second main surfaces 2 and 3 of the metal plate 4, respectively. Laminated. A surface conductor 7 is formed on the ceramic green layer to be the first ceramic layer 5, and if necessary, the ceramic green layer to be the first and second ceramic layers 5 and 6 has an internal A conductor is formed. Subsequently, a baking process is implemented. As a result, the ceramic green layer is sintered to become the first and second ceramic layers 5 and 6, and the metal base substrate 1 is obtained.

  In order to join the metal plate 4 and each of the ceramic layers 5 and 6 with respect to the manufacturing method described above, each of the ceramic layers 5 and 6 has a laminated structure and has a main surface direction in the firing step as follows. It is preferable to take measures so that the shrinkage at the bottom can be suppressed.

  First, a metal plate 4 is prepared, and a first ceramic slurry containing a low-temperature sintered ceramic material and a second ceramic material that does not sinter at the sintering temperature of the low-temperature sintered ceramic material are included. A ceramic slurry is prepared.

  Next, on the first main surface 2 of the metal plate 4, the first ceramic green layer made of the first ceramic slurry to be the first ceramic layer 5 and the second ceramic made of the second ceramic slurry. A green layer is placed.

  On the other hand, on the second main surface 3 of the metal plate 4, the first ceramic green layer made of the first ceramic slurry to be the second ceramic layer 6 and the second ceramic green made of the second ceramic slurry. Layers are placed. The first ceramic green layer and the second ceramic green layer that are to become the second ceramic layer 6 are shaped to provide the frame-shaped portion 8.

  Here, the above-described surface conductor 7 and, if necessary, the internal conductor are provided in a specific ceramic green layer.

  In carrying out the above-mentioned steps, preferably, the first ceramic slurry is formed into a sheet form on the ceramic green sheet obtained by forming the first ceramic slurry into a sheet form, thereby forming the first ceramic slurry. After obtaining a composite green sheet in which the green layer and the second ceramic green layer are overlaid, the composite green sheet is laminated on the first and second main surfaces 2 and 3 of the metal plate 4 as required, Crimping is performed.

  In place of the above method, a first ceramic green sheet obtained by forming the first ceramic slurry and a second ceramic green sheet obtained by forming the second ceramic slurry are made of metal. Alternatively, the first and second main surfaces 2 and 3 of the plate 4 may be alternately stacked. Alternatively, the formation of the second ceramic green layer and the formation of the first ceramic green layer may be repeated on the first ceramic green sheet.

  Next, a step of simultaneously firing the first and second ceramic green layers to be the first and second ceramic layers 5 and 6 and the metal plate 4 is performed. In this co-firing step, the low-temperature sintered ceramic material contained in the first ceramic green layer is sintered. Further, a part of this low-temperature sintered ceramic material flows into the second ceramic green layer, solidifies the hardly sinterable ceramic material contained in the second ceramic green layer, Densify.

  Since the second ceramic green layer does not substantially shrink in the main surface direction in the firing step, the second ceramic green layer acts to suppress shrinkage in the main surface direction of the first ceramic green layer. Therefore, shrinkage in the main surface direction of the entire laminate portion composed of the first and second ceramic green layers on the metal plate 4 is advantageously suppressed. For this reason, it is possible to make it difficult to cause peeling between the first or second ceramic green layer and the metal plate 4 due to shrinkage.

  If the thickness of the second ceramic green layer is 0.05 times or more than the thickness of the first ceramic green layer, the shrinkage suppressing effect during firing by the second ceramic green layer can be sufficiently exerted, As a result, it has been found that peeling between the first or second ceramic green layer and the metal plate 4 due to shrinkage can be made more difficult to occur.

  In this co-firing step, not only the first ceramic green layer can be densified, but also a part of the low-temperature sintered ceramic material contained in the first ceramic green layer is sufficiently contained in the second ceramic green layer. As a result, the second ceramic green layer can be densified, so that the thickness of the second ceramic green layer is 0.4 times or less the thickness of the first ceramic green layer. It is preferable to make it thin.

  Further, the second ceramic green layer is not yet densified at the degreasing stage in the firing process, and therefore provides a discharge path for the gas generated as a result of degreasing. Therefore, good degreasing properties are ensured in the entire laminated body portion composed of the first and second ceramic green layers. In particular, since the degreasing property in the vicinity of the metal plate 4 is also excellent, it is possible to suppress the occurrence of peeling at the portion due to residual carbon.

  It has been found that the thickness of the second ceramic green layer is preferably 0.06 times or more of the thickness of the first ceramic green layer in order to ensure the above-described good degreasing property more reliably. .

  In this way, the metal base substrate 1 is obtained. In the metal base substrate 1, the metal plate 4 and each of the ceramic layers 5 and 6 are brought into a bonded state without separately forming a bonding glass layer. At this time, a thin glass layer of about 1 to 5 μm may be formed between the metal plate 4 of the metal base substrate 1 and each of the ceramic layers 5 and 6 in the firing process.

  In the above-described manufacturing method, the first ceramic green layer made of the first ceramic slurry containing the low temperature sintered ceramic material and the hardly sinterable ceramic material that does not sinter at the sintering temperature of the low temperature sintered ceramic material. The second ceramic green layer made of the second ceramic slurry containing, but instead of this, two or more kinds of ceramic green layers having different shrinkage start temperatures are used, and the principal plane directions of the ceramic layers 5 and 6 are used. You may suppress contraction to. Specifically, by laminating a ceramic green layer with a relatively low shrinkage start temperature and a ceramic green layer with a relatively high shrinkage start temperature, the latter shrinks in the main surface direction in the temperature range where the former shrinks. In the temperature range in which the latter contracts, the former, which has completed the contraction, suppresses the contraction in the main surface direction of the latter, thereby suppressing the contraction in the main surface direction of the ceramic layers 5 and 6.

  In addition, regarding the manufacturing method described above, in order to join the metal plate 4 and each of the ceramic layers 5 and 6, a bonding glass layer of about several tens of μm is previously provided between the metal plate 4 and each of the ceramic layers 5 and 6. A manufacturing method may be employed in which the bonding glass layer is melted and the bonded state is achieved in the firing step.

  However, in this case, since the bonding glass layer can act as a relaxation layer, warpage can be suppressed to some extent as compared to the case where the bonding glass layer is not formed in advance.

  In addition, the metal base substrate 1 is subjected to a firing process in a state where the metal plate 4 and the fired ceramic layers 5 and 6 are overlapped, whereby the joining state of the metal plate 4 and each of the ceramic layers 5 and 6 is changed. It can also be manufactured by the method obtained. In this case, the ceramic layers 5 and 6 may be made of a low-temperature sintered ceramic as described above, or may be made of a high-temperature sintered ceramic such as aluminum nitride. However, in this case, the ceramic layers 5 and 6 are not substantially contracted during firing, and the firing temperature for bonding can be made relatively low, so that warping is suppressed to some extent.

  Therefore, the present invention is particularly effective when the unfired low-temperature sintered ceramic layer is co-fired with the metal plate 4, and more specifically, the unfired low-temperature fired ceramic layer is made of metal without using the bonding glass layer. This is most effective when fired simultaneously with the plate 4.

  Next, with reference to FIG. 2, a metal base substrate 1a according to a second embodiment of the present invention will be described. In FIG. 2, elements corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The metal base substrate 1a shown in FIG. 2 is characterized by the form of the second ceramic layer 6a. The second ceramic layer 6a includes at least a frame-shaped portion 8a positioned along the frame-shaped region on the second main surface 3, and the second main surface 3 in a region surrounded by the frame-shaped portion 8a. 1 is the same as the second ceramic layer 6 shown in FIG. 1 in that it has an opening 9a that exposes a part thereof, but differs from that shown in FIG. 1 in the following points.

  The second ceramic layer 6a shown in FIG. 2 further includes a lattice portion 10 extending in a lattice shape in a region surrounded by the frame portion 8a, and the openings 9a are formed between the lattices of the lattice portion 10 and Distributed in islands. According to such a configuration, in addition to the warp suppressing action by the frame-like part 8a, the warp suppressing action by the grid-like part 10 can be exhibited, and high heat dissipation is realized in the grid-like part 10. be able to.

Other configurations and manufacturing methods of the metal base substrate 1a shown in FIG. 2 are substantially the same as those of the metal base substrate 1 shown in FIG. As in the case of the metal base substrate 1 shown in FIG. 1, the surface of the metal base substrate 1a shown in FIG. 2 is located outside the main surface 3.

  The metal base substrates 1 and 1a described above with reference to FIGS. 1 and 2 are used in a state as shown in FIG. 3, for example. FIG. 3 shows an electronic component device 11 configured using the metal base substrate 1a shown in FIG.

  Referring to FIG. 3, semiconductor element 12 such as an IC is mounted on first ceramic layer 5 of metal base substrate 1a. The semiconductor element 12 is electrically connected to a specific one of the surface conductors 7 by bonding wires 13.

  On the other hand, a heat sink 14 is disposed on the second ceramic layer 6a side of the metal base substrate 1a. The heat sink 14 is made of a metal having a good thermal conductivity, and is mechanically joined to the metal plate 4 through a solder 15 introduced into an opening 9a provided in the second ceramic layer 6a and thermally. Combined.

  In use, the heat generated in the semiconductor element 12 is transmitted to the metal plate 4 via the first ceramic layer 5 and is radiated from the metal plate 4 to the heat sink 14 via the solder 15 and the like.

  Next, experimental examples carried out based on the present invention will be described.

1. Experimental example 1
[Production of composite green sheet]
BaCO ₃ , Al ₂ O ₃ , and SiO ₂ powders were prepared, and the mixed powder obtained by mixing these powders was calcined for 120 minutes at a temperature of 840 ° C., whereby BaO: 37.0 wt%, Al ₂ O ₃ A raw material powder having a content ratio of 11.0% by weight and SiO ₂ : 52.0% by weight was produced.

Next, the raw material powder: 90.0 parts by weight, MnCO ₃ powder: 7.0 parts by weight, Mg (OH) ₂ powder: 1.0 part by weight, and TiO ₂ powder: 2.0 parts by weight Were mixed in an organic solvent to which was added, and then a resin and a plasticizer were added and further mixed to obtain a first ceramic slurry containing a low-temperature sintered ceramic material.

  Next, after defoaming the first ceramic slurry, a ceramic green sheet to be the first ceramic green layer having a thickness of 80 μm was prepared by a doctor blade method.

On the other hand, glass powder composed of BaO, Al ₂ O ₃ , SiO ₂ , MgO, B ₂ O ₃ , and Li ₂ O and Al ₂ O ₃ powder are mixed at a ratio of 40 parts by weight to 60 parts by weight. After mixing in the added organic solvent, a resin and a plasticizer were added later and further mixed to obtain a second ceramic slurry containing a hardly sinterable ceramic material.

  Next, after defoaming the second ceramic slurry, it was formed into a 10 μm thick sheet by the doctor blade method on the ceramic green sheet described above. In this way, a composite green sheet was obtained in which the first ceramic green layer provided by the ceramic green sheet and the second ceramic green layer formed from the second ceramic slurry were overlaid.

  It has been confirmed that the ceramic molded body obtained by molding the second ceramic slurry alone is not sintered even when fired under the firing conditions described later.

[Preparation of metal base substrate before firing]
FIG. 4 shows a metal base substrate 21 according to the sample 1 to be manufactured in Experimental Example 1.

  A copper plate 22 having a length of 100 mm, a width of 50 mm, and a thickness of 0.8 mm was prepared as a metal plate. In order to form the first ceramic layer 24 on the upper surface 23 of the copper plate 22, three composite green sheets were laminated, and further, an electrode-forming copper foil 25 having a thickness of 0.2 mm was laminated thereon. On the lower surface 26 of the copper plate 22, three composite green sheets cut into a predetermined shape so as to give a frame-shaped portion 28 and an opening 29 were laminated in order to form the second ceramic layer 27. In the sample 1, the ratio of the width “W1” of the frame-shaped portion 28 shown in FIG. 4 to the length of 100 mm of the copper plate 22 and the width “W2” of the frame-shaped portion 28 shown in FIG. The cut shape of the composite green sheet was changed so that the ratio of 22 to the width of 50 mm was both “10%” shown in the “W ratio” column of Table 1. Next, a pressing process was performed, and the metal base substrate 21 was obtained before firing.

  FIG. 5 shows a metal base substrate 31 according to the sample 2 to be manufactured in this experimental example 1.

  In order to form the first ceramic layer 34 on the upper surface 33 of the copper plate 32 having a length of 100 mm, a width of 50 mm, and a thickness of 0.8 mm as described above, three composite green sheets are laminated, and further thereon. A copper foil 35 for forming an electrode having a thickness of 0.2 mm was laminated. In order to form the second ceramic layer 37 on the lower surface 36 of the copper plate 32, three of the composite green sheets were laminated, and further, a heat radiating copper foil 38 having a thickness of 0.2 mm was laminated thereon. In Sample 2, after the firing described later, according to the same expression method as in Sample 1, the “W ratio” in Table 1 is “50%”. Next, a pressing process was performed, and the metal base substrate 31 was obtained before firing.

  Further, although not shown in the drawing, as the sample 3, three composite green sheets are used to form a first ceramic layer on the upper surface of a copper plate having a length of 100 mm, a width of 50 mm, and a thickness of 0.8 mm as described above. The electrode forming copper foil having a thickness of 0.2 mm is further laminated thereon, and on the lower surface of the copper plate, any of the second ceramic layer, the electrode forming copper foil and the heat radiating copper foil is provided. A metal base substrate that was not formed was prepared before firing. In Sample 3, after the firing described later, according to the same expression method as in Sample 1, the “W ratio” in Table 1 is “0%”.

[Baking]
The metal base according to Sample 1 shown in FIG. 4 was sintered by firing the metal base substrates according to Samples 1, 2, and 3 before firing at a temperature of 980 ° C. for 180 minutes in a reducing atmosphere. The substrate 21, the metal base substrate 31 according to the sample 2 shown in FIG. 5, and the metal base substrate according to the sample 3 (not shown) were obtained.

[Evaluation]
-Warpage The warpage of the metal base substrate according to Samples 1, 2, and 3 after firing was measured with a laser displacement meter. The measurement results are shown in the “warp” column of Table 1.

-Thermal resistance The thermal resistance of the metal base substrates 21 and 31 was measured with a thermal resistance measuring device. The measurement results are shown in the column of “thermal resistance” in Table 1. The value of “thermal resistance” shown in the table is a ratio when the thermal resistance value of the sample 2 is 100.

  As can be seen from Table 1, sample 1 was able to achieve both low thermal resistance and small warpage. On the other hand, in Sample 2, the warpage could be suppressed to a small value, but the thermal resistance increased. In Sample 3, the thermal resistance could be kept low, but the warpage could not be kept small.

2. Experimental example 2
[Production of composite green sheet]
In the same manner as in Experimental Example 1, a composite green sheet was obtained.

[Preparation of metal base substrate before firing]
Instead of the composite green sheet to be the second ceramic layer 27 in the metal base substrate 21 according to the sample 1 manufactured in Experimental Example 1, a frame-shaped portion and a lattice-shaped portion in which openings are distributed in an island shape are provided. Three composite green sheets cut into a predetermined shape were laminated. Next, a pressing step was performed to obtain a state before firing of the metal base substrate.

[Baking]
The metal base substrate before firing was fired under the same conditions as in Experimental Example 1 to obtain a sintered metal base substrate as Sample 4.

[Evaluation]
As in the case of Experimental Example 1, “warp” and “thermal resistance” were evaluated.

  As a result, according to the sample 4, it was possible to further suppress the warp while keeping the thermal resistance low as compared with the above-described sample 1 in which the lattice-shaped portion was not formed.

DESCRIPTION OF SYMBOLS 1,1a Metal base board | substrate 2 1st main surface 3 2nd main surface 4 Metal plate 5 1st ceramic layer 6, 6a 2nd ceramic layer 8, 8a Frame-shaped part 9, 9a Opening 10 Grid-shaped part

Claims (3)

A metal plate having first and second main surfaces facing each other;
A first ceramic layer formed on the first main surface of the metal plate;
A second ceramic layer formed on the second main surface of the metal plate,
The second ceramic layer includes at least a frame-shaped portion positioned along the frame-shaped region on the second main surface, and one of the second main surfaces in a region surrounded by the frame-shaped portion. part have a opening for exposing the surface of the opening side of the metal base substrate is positioned outside the said second main surface,
Metal base substrate.   The metal base substrate according to claim 1, wherein the frame-shaped portion is positioned so as to cover the peripheral edge without leaving a margin in the peripheral edge of the second main surface.   The second ceramic layer further includes a lattice-like portion extending in a lattice shape in a region surrounded by the frame-like portion, and the openings are formed between the lattices of the lattice-like portion and distributed in an island shape. The metal base substrate according to claim 1 or 2.

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